For some time, it has been known that cells, human cells, can be treated to "spread" the chromosomes so that they might be analyzed under a microscope for possible defects. The breakthroughs in cytogenetic techniques have been of landmark proportions in the last few decades. Examples include introduction of the hypotonic treatment in the 50s (HSu 1952), use of PHA to stimulate lymphocyte culture in the 60s (Nowell et al. 1960a; Nowell et al. 1960b), the ability to induce high resolution banding (Yunis et al. 1976) and development of in situ culture methods (Peakman et al. 1979; Spurbeck et al. 1988a) and robotic harvesting (Spurbeck et al. 1988b) during the 70s and 80s.
In spite of these remarkable advancements in cytogenetic techniques, consistency of optimum spreading of chromosomes remains a major problem. The consistency with which one could obtain optimum chromosome spreading of cytogenetic specimens has been a major concern.
From an examination of prior art, it is apparent that incubators used to grow cell cultures using live cells are unsuited for cytogenetic analysis. (It is understood that cell culturing is carried out in Petri dishes or other shallow vessels capable of holding a liquid such as a cell nutrient. The very name "incubator" implies sustenance of life.)
U.S. Pat. Nos. 4,572,427 (Selfridge et al.); 4,689,303 (Kraft et al.); 4,696,902 (Bisconte); 4,701,415 (Dutton et al.) and 4,923,816 (Heeg et al.) disclose and seem to typify such incubators. The incubators disclosed in such patents appear suitable for use by but one person at a time and require door opening to place the cell cultures.
The Selfridge et al. and Dutton et al. patents describe incubators said to be useful in growing cell cultures. Chamber atmosphere is controlled as to concentrations of one or more constituent gases (e.g., oxygen and carbon dioxide) and as to humidity.
The Kraft et al. patent discloses an incubator for treating cultures placed on microplates. Several microplates are placed on each of several vertically-spaced trays and each tray has an angularly-upturned lip which juts outward beyond the lip of the tray above it. Some of the air circulating past the lips is diverted by each lip and thereby directed across the surface of the microplates on that tray. In other words, the direction of air flow differs, depending upon what area of the incubator interior is being considered.
The Kraft et al. incubator has carbon dioxide and oxygen sensors and the patent mentions that temperatures in the range of 37.degree. C. (99.degree. F.) to 50.degree. C. (122.degree. F.) are used for incubation. Gas flow rates of 250 feet (760 cm.) per minute and 1000 feet (3050 cm.) per minute are also mentioned. The enclosure is of the double-door type.
The gassing incubator described in the Heeg et al. patent has two doors, both of which are transparent. Such patent implies that humidities of 90% and higher are used for cell culturing.
The Bisconte patent also describes an apparatus for cell culture. Cells to be cultured are in each of several storage devices within the enclosure, with each storage device holding multiple culture containers. Each container is in a respective sealed compartment and as a consequence, cells being cultured are shielded from direct air flow. Such shielding (and the use of high humidity as noted above) seemingly is to prevent drying of the culture. In its mention of how high air flow rates "tend to dry out biological culture media," the Dutton et al. patent appears to be in support of the idea that drying is undesirable when incubating cells.
Certainly, incubators are suitable for growing cell cultures but from the foregoing, it seems apparent that incubators are inappropriate for cell drying. A chamber configured for cytogenetic analysis and cell drying would be an important advance in the art.